National Atmospheric Release Advisory Center Dispersion Modeling of the Full-scale Radiological Dispersal Device (FSRDD) Field Trials

Abstract

The results of the National Atmospheric Release Advisory Center (NARAC) model simulations are compared to measured data from the Full-Scale Radiological Dispersal Device (FSRDD) field trials. The series of explosive radiological dispersal device (RDD) experiments was conducted in 2012 by Defence Research and Development Canada (DRDC) and collaborating organizations. During the trials, a wealth of data was collected, including a variety of deposition and air concentration measurements. The experiments were conducted with one of the stated goals being to provide measurements to atmospheric dispersion modelers. These measurements can be used to facilitate important model validation studies. For this study, meteorological observations recorded during the tests are input to the diagnostic meteorological model, ADAPT, which provides 3-D, time-varying mean wind and turbulence fields to the LODI dispersion model. LODI concentration and deposition results are compared to the measured data, and the sensitivity of the model results to changes in input conditions (such as the particle activity size distribution of the source) and model physics (such as the rise of the buoyant cloud of explosive products) is explored. The NARAC simulations predicted the experimentally measured deposition results reasonably well considering the complexity of the release. Changes to the activity size distribution of the modeled particles can improve the agreement of the model results to measurement.

Aerial Mobile Radiation Survey Following Detonation of a Radiological Dispersal Device

“…The maps created from both surveys display this effect. Measurement of this kind of non-monotonic behavior in the plume profile is important, as simple models of RDD behavior such as those presented in this volume (Purves and Parkes 2016;Lebel et al 2016;Neuscamman and Yu 2016) do not predict these details. Significant depositions do not extend as far as was found with the first blast, with significant activity concentration measured out to about 1,200 m from ground zero.…”

Introduction to the Special Issue on Experiments Involving the Outdoor Energetic Release of Radioactive Materials

“…Comparison of dispersion model results to the FSRDD Field Trial measurements and analysis of model performance are presented in four papers. These dispersion modeling papers are by Purves and Parkes (2016), Neuscamman and Yu (2016), and two papers by Lebel et al (2016a and b).…”

Deposition Measurements From the Full-Scale Radiological Dispersal Device Field Trials

“…For example, in their respective papers, Purves and Parkes (2016), Lebel et al (2016a and b), and Neuscamman and Yu (2016) each use different atmospheric dispersion models to simulate the dispersion of radiological materials from these tests. In Arya (1999), however, a simple analytical treatment is presented that describes the cumulative deposition of material based on the Gaussian dispersion model and the assumption that the deposition flux, F d , at any point is proportional to the ground-level air concentration, c o , and a constant deposition velocity, v d , according to eqn (1):…”

“…The in situ gamma measurements provide the gamma dose-rate due to the ground shine produced by the deposited radioactive contamination. These measurements are complementary and can be used for cross-comparison with other data sets, such as the helicopter-based aerial radiation surveys (Sinclair et al 2016), as well as for comparison with dispersion models (Lebel et al 2016a;Purves and Parkes 2016;Neuscamman and Yu 2016).…”